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crashtcs

unstable idle

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I have a 98 YZ400, which I recently bought used so I don't know it's history, and the idle is very strange. It seems to idle good from a cold start, but runs fast when warmed up, and will occaisionaly drop for a brief period (about 30 seconds) then climb back up. I was thinking it is an air leak, but I havn't been noticed any changes to the idle using carb cleaner around the top end. It does seem to be running a little lean though -- I get some backfiring.

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Craig

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Check the rubber boot on the hot start button, I had the same symptoms and all it took was pushing the boot back over the lip.

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Just checked the hot start plunger and the boot was on all the way. The plunger shaft is a little bent, but seems to be operating normal.

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Craig

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It may just be running lean in the slow circuit. Open the fuel screw in 1/4 turn increaments until it goes away. If you get past 2 1/2 turns go one size up on the pilot jet and start over. Stock pilot is a 45. I run a 48 in my 99' 400.

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SHN

99'YZ-400 (Mine)

00' TT-R 125 (Hers)

91' KX-125 (Son #1)

93' CR-80 (Just sold it. Looking for another TTR125 for Son #2)

99' PW-80 (Son #3)

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Definately sounds like lean condition.

Idle hangs = lean

Idle bogs = rich

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